According to one known embodiment, an electronic device includes, in a stacked configuration, a support wafer, an integrated-circuit chip mounted on a front face of this support wafer and including a sensor in its front face, and a protective wafer mounted above this front face. This stack is generally surrounded by an encapsulation block.
Particularly in the case in which the sensor is an optical sensor located on the same side as the protective wafer, selected to be made of a transparent material, for example glass, there are attendant difficulties for obtaining a free and leaktight space between the front face of the chip and the protective wafer.